As to an acoustic apparatus having a super-directivity by using a parametric loudspeaker, in order to separate a listening area for a listener to listen sounds from a non-listening area not to listen sounds, various methods are proposed. For example, it is desired that the listening area and the non-listening area are separated along a propagation direction of sound. In this case, by using two parametric loudspeakers from which sound waves having the same characteristic of sound pressure-distribution are radiated, the sound waves from respective parametric loudspeakers are interfered. As a result, sound pressures of the sound waves at the non-listening area are cancelled.
However, in above-mentioned method, a cancel amount of the sound pressure becomes large at not only the non-listening area but also the listening area. Accordingly, at the listening area, it is difficult that a sound pressure of a synthesis sound interfered is sufficiently maintained.